Video‐based analysis for facial skin appearance with automatic face tracking

In this article, a video‐based analysis for facial skin appearance with an automatic face tracking technique is proposed. The change of skin appearance under various illuminations is observed by illuminating the face from various light source positions, and the changes in facial appearance are recorded as a video stream during this measurement. The recorded video stream is then analyzed to obtain the bidirectional reflectance distribution function (BRDF) at each position of the facial skin. Automatic face tracking is necessary to compensate the facial movement in order to obtain an accurate BRDF measurement at each position. Since conventional face tracking techniques cannot be used for a face illuminated from various light source positions, a new face tracking technique that is robust to the various face shadings has been developed. Experimental studies show the effectiveness of both the proposed video‐based analysis technique and the automatic face tracking technique. © 2008 Wiley Periodicals, Inc. Col Res Appl, 33, 477–484, 2008     

Diffuse reflectance‐factor measurements of rose petals

The diffuse reflectance factor for different colored rose petals is measured as a function of wavelength using a high resolution optical spectrometer. The tristimulus values, the CIE chromaticity coordinates, the dominant wavelength and purity, the CIE whiteness index, the tint index, the CIE 1976 LAB coordinates, as well as CIELAB hue‐angle and chroma are reported. The data on diffuse reflectance factor are presented in the 390?800 nm range at intervals of 10 nm. Using the data, one can generate the perceived color of the roses and the color coordinates in different illuminating light sources and environments. The present data will be useful for the color characterization of flowers, realistic rendering of flowers in computer graphics, color photography, and in the development of filters for color photography. © 2010 Wiley Periodicals, Inc. Col Res Appl, 2011     

可见光响应的Bi-TiO_2的制备及其对间苯二酚的降解作用

以钛酸四丁酯、硝酸铋为原料,采用水热法制备铋掺杂TiO2光催化剂（Bi-TiO2）。所得材料用X射线衍射、透射电子显微镜、X射线能谱、X射线荧光光谱、UV–Vis漫反射等测试手段分析。结果显示水热法可以直接合成锐钛型纳米TiO2。铋在TiO2中的掺杂方式为Bi3＋替位取代TiO2中Ti4＋。样品具有较大的比表面积,其最大达31.2 m2/g。铋掺杂能引起TiO2光催化剂的吸收光谱明显红移,从而具备较好的可见光响应性。以降解间苯二酚为探针反应研究其可见光催化性能,纯TiO2光催化活性极低,而Bi-TiO2具有较高的可见光催化性能,当铋掺杂量为1.00%时光催化性能最佳。UV–Vis光谱和高效液相色谱显示间苯二酚在70W金卤灯下反应120min能完全分解。     

Proceedings of the Inter-Society Color Council Technical Conference “Instrumental Colorant Formulation 1976” Williamsburg,Virginia. III Problems of Fluorescence in Colorant Formulation

The presence of fluorescence in samples to be matched and in dyes to be used for matching requires precautions in measurement and in computation. Measurement of conventional reflectance may cause serious errors of formulation. Standard procedures for calculating matches are usually based on the additivity of the K/S values. In contrast, contributions of fluorescence have to be added to the spectral radiance factors. Specifications for a rigorous procedure are presented. Merits and shortcomings of currently used methods are discussed. An approximation making use of negative Kubelka-Munk coefficients is set forth. It is valid only for applications of a single fluorescent colorant which may be shaded slightly by minor additions of other colorants.     

Analysis of aldehydic lipid peroxidation products by TLC/densitometry

We have explored the use of thin-layer chromatography (TLC)/densitometry in both the reflectance and fluorescence mode for quantitation of specific products of lipid peroxidation. Aldehydic peroxidation products were generated by exposure of arachidonic acid to iron and ascorbic acid for 24 hr. Several methods for the quantitative analysis of peroxidation products by TLC/densitometry were compared using two different aldehydespecific derivatizing reagents, namely dinitrophenylhydrazine (DNPH) and cyclohexanedione (CHD). DNPH hydrazones of the arachidonic acid-peroxidation products, upon TLC separation on silica gel, revealed prominent alkanal and hydroxyalkenal bands. Reverse phase high performance liquid chromatography confirmed that the primary alkanal component was hexanal, while the primary hydroxyalkenal was 4-hydroxynonenal. Semiquantitative methods for the direct analysis of these products by TLC/densitometry were worked out based on the use of external hydrazone standards. TLC/densitometry (fluorescence mode) was used to measure CHD adducts of aldehydes by forming the derivatives in the presence of decanal (used as an internal standard) and separating the derivatives by reverse phase TLC. Hexanal-CHD was detectable upon application of 0.5 nanomoles while 4-hydroxynomenal showed a lower response and was detectable with 10 nanomoles. Using appropriate response factors, hexanal and 4-hydroxynonenal were measured in the aldehyde sample from arachidonic acid and results were similar to those obtained by the DNPH method. Similar approaches were used to analyze the peroxidation products of docosahexaenoic acid (24-hr exposure) The DHA peroxidation products contained extremely low levels of alkanals, while polar aldehydes and hydroxyalkenals were prominent. Formation of alkanals, osazones, hydroxyalkenals and phospholipid aldehydes from iron-exposed microsomes was also demonstrated. Uses and limitations of these methods of aldehyde measurement are discussed.     

DETERMINATION OF REFLECTANCE OF WHITE ENAMEL FRITS BY TURBIDITY METHOD*

A method for the determination of the reflectance of powdered frits is described. Results obtained by this method show a high correlation with the results of standard reflectance tests, particularly when frits are fused at enameling temperatures. The method consists essentially of suspending 0.4 cc. of sample, sized between 270- and 325-mesh, in 10 cc. of clear kerosene and measuring by means of a photoelectric cell the decrease in light transmitted as compared with the light transmitted by kerosene itself. The Cenco-Sheard-Sanford photelometer was used for these measurements.     

The effect of gloss on color

A model was developed for the effect of gloss on reflected color, taking the measurement geometry of the color measuring device into account. It considers the total front surface reflectance of a given sample to be independent of gloss and determined only by its refractive index and the angle of the incident beam. Although the total front surface reflectance is fixed, its specular component increases (and the diffuse component decreases) with increasing sample gloss. Therefore, the diffuse reflectance factor measured by a spectrophotometer decreases with sample gloss. In this article, a defined curve was fitted to the measured reflectance factor of black xerographic print samples having a range of gloss values for the 0/45 and diffuse spectrophotometer geometries, and this curve was used to predict the CIELAB color values for samples of the other colors at various gloss levels. The predicted color was compared to the measured color for cyan, magenta, yellow, red, green, and blue images that spanned a wide range of gloss. The RMS color error between the predicted and measured color of all of these images was found to be about 3 CIELAB ΔE* units. © 1999 John Wiley & Sons, Inc. Col Res Appl, 24, 369–376, 1999     

Assessment of whiteness and tint of fluorescent substrates with good interinstrument correlation

White is primarily a sensation like blue, green, or red and, as such, is not measurable directly. Only a physical property, the spectral reflectance of a sample, can be measured directly. But this is not a standard, fixed quantity; it depends on a number of individual properties of the measuring instrument used. the entire geometry of the illuminating chamber—generally speaking a sphere is used for samples with a structured surface—is incorporated in the measuring results. the size of the aperture and the exclusion or inclusion of gloss also influence reflectance. High whiteness is obtainable only with the aid of fluorescent whitening agents [FWAs], and is hence a fluorescent color, which demands specific qualities of the illumination. the sample illumination must be identical with that for which the colorimetric values have been calculated. Nowadays, however, this is usually standard illuminant D65, which can be simulated only approximately in measuring instruments. In addition, all lamps used are subject to changes in spectral energy distribution. the problem is how to obtain constant, comparable results, namely whiteness, tint, and lightness for fluorescent materials using measuring instruments of different designs incorporating different means of simulating standard illuminant D65 or other D illuminants. This article presents a method that has been in use in industry for about 20 years. the method in question comprises two parts: first, on the hardware side, sample illumination that has to meet specific requirements, match the UV excitation required, and remain stable; second, on the software side, the two critical dimensions of whiteness and tint are calculated indirectly from the measuring results. Only in this way is it possible to achieve a large measure of comparability between different instruments. In principle, the method is also suitable for different illuminants and for any white preference. In all other methods of assessment the parameters are not matched to the instrument characteristics. If the results obtained with different measuring instruments are to be compared, difference values have to be used, entailing the need for standards and involving all the drawbacks associated with them.     

Plasmonic near-field in the vicinity of a single gold nanoparticle investigated with fluorescence correlation spectroscopy

We proposed the estimation of the plasmonic near-field volume in the vicinity of a single gold nanoparticle, and observed experimentally the near-field variation due to a change in the polarization of the illuminating light. Under total-internal-reflection illumination, the plasmonic near-field volume is varied by tuning the polarization of the excitation light. The variation in the optical near-field around a single gold nanoparticle was simulated theoretically with a finite-difference time domain method, and was characterized experimentally employing a fluorescence correlation spectroscopy technique. The experimental results are in agreement quantitatively with the theoretical analysis. These results are highly relevant to important efforts to clarify the interaction between the emitter and the plasmonic antenna, and should be helpful in developing a plasmonic-enhanced total-internal-reflection fluorescence imaging microscope.     

Practical method for measuring printed colors on FWA‐treated paper

The virtual fluorescent standard (VFS) method is a new approximation method for the practical measurement of the colorimetric properties of an object treated with fluorescent whitening agent (FWA). The essential requirement of the VFS method is that the bi‐spectral characteristics of the VFS must be similar in curve shape to those of the object to be measured. In the case of an object printed on an FWA‐treated substrate, the bi‐spectral characteristics will vary depending on not only the substrate but also the printed ink films. In this study, two simplified VFS methods, one using the bi‐spectral characteristics of the substrate and the other using those of typical paper as the VFS instead of those similar to each object, were evaluated. The evaluation was performed using two instrument models for the VFS method with the different illuminations with five sets of 13 samples printed in different colors by five different printer/paper combinations. In this evaluation, the total spectral radiance factor of each sample was obtained by simulated measurement, that is, it was calculated based on the bi‐spectral radiance factor of the sample and the spectral power distributions of the light source of the instrument. The total spectral radiance factor of each sample under D50 obtained using both VFS models and CIE L*a*b* values derived therefrom were compared with those by the reference model with ideal D50 illumination. Although the samples are limited, the results shows that both simplified VFS methods remarkably reduce the errors due to fluorescence when compared to the conventional method. © 2011 Wiley Periodicals, Inc. Col Res Appl, 2012     

Transferring the 45/0 spectral reflectance factor scale

The accuracy of spectrophotometric measurements is limited by the standards that are used to calibrate the instrument. Therefore, the procedure used in transferring the spectral reflectance factor scale from one material to another for use in calibration must induce the minimum amount of error. the Munsell Color Science Laboratory has been transferring the spectral reflectance factor scale to calibration materials using a statistical method to correct for the most pervasive systematic errors in the measurement process. This method is based on a statistical procedure in which a set of systematic spectrophotometric errors are estimated based on the measurement of seven NIST primary standards and corrected in subsequent measurements. the optimization of the spectral reflectance factor scale to NIST standards minimizes the induced error. the average reflectance factor error consistently found between the corrected measurements of the NIST standards and their certificate values have been 0.0006 and the average δ_ab has been on the order of 0.2.     

Reflectance versus transmittance: The effects of light scattering on red colorants (carmine,amazonian red annatto,and peruvian cochinilla rojo and rosada) in biological,textile, and museum science

Spectra were strongly influenced by the way they were measured but, in general, carmine, cochinilla rojo and rosada, and red annatto all had strong transmittance and reflectance of red light (>640 nm), and strong absorbance of green light (520–560 nm). Spectra for carmine and cochinilla rosada both had secondary peaks for transmittance and reflectance (around 420 and 450 nm for stains, respectively), whereas secondary peaks were not found for cochinilla rojo and red annatto. Both cochinilla rosada and rojo stained skeletal myofibers, but only cochinilla rojo withstood alcohol dehydration and mounting as a general stain for paraffin sections. Carmine was ideal for enhancing the appearance of pork because its spectrum was similar to that of myoglobin, thus increasing the absorbance of green light without producing unnatural colors like cochinilla rosada and rojo. Cochinilla rojo dyed alpaca wool orange, and cochinilla rosada dyed wool pink. The scale of the measurement (micro‐ vs. macroscopic) and the type of measurement (transmittance vs. reflectance) were of minor importance in colorimetry, whereas a major effect was detected for light scattering in the sample. A ratio indicative of scattering (400/700 nm) was strongly correlated with chromaticity coordinate x, r = ?0.86, P < 0.001, n = 18. © 2013 Wiley Periodicals, Inc. Col Res Appl, 39, 599–606, 2014     

原子荧光法测定土壤中的砷和汞元素含量

原子荧光法在测定土壤中的砷与汞时,能够以自身高灵敏度、光谱干扰少、测量步骤简单等优势来提高测定的实效性,进而快捷准确的实现测定工作,特别适用于痕量元素分析及多元素的同时测定。在测定时,需要以微波消解技术来实现对试样的消解处理,以原子荧光光度计来实现土壤中两种元素的同时测定。通过对原子荧光法在同时测土壤中砷和汞元素含量中的应用方法和步骤进行相关探讨分析。     

Photoacoustic and photothermal spectroscopy — novel tools for the analysis of particulate matter

Measurments on powders using photoacoustic (PAS) and photothermal (PTS) spectroscopic techniques are described. These methods avail themselves of the heat that is generated in a sample upon irradiation, which can be used to analyse and identify the sample through its absorption spectrum.Three different techniques have been used to extract the required information: (i) By having the specimen inside a chamber, illuminating it through a window and recording the resulting pressure variations; (ii) similarly, only having the sample outside the chamber but in contact with a membrane in the chamber wall: (iii) by measuring the extra thermal emission from the object when heated upon illumination. The advantages of using PAS and PTS methods to powder analysis are presented, and their applications to in-stream measurements of particulate solid properties are discussed.     

Absorption and reflection of infrared radiation by polymers in fire‐like environments

In large‐scale fires, the input of energy to burning materials occurs predominantly by radiative transfer. The in‐depth (rather than just surface) absorption of radiant energy by a polymer influences its ignition time and burning rate. The present investigation examines two methods for obtaining the absorption coefficient of polymers for infrared radiation from high‐temperature sources: a broadband method and a spectral method. Data on the total average broadband transmittance for 11 thermoplastics are presented (as are reflectance data), and the absorption coefficient is found to vary with thickness. Implications for modeling of mass loss experiments are discussed. Copyright © 2011 John Wiley & Sons, Ltd.     

反射式电子书阅读器对比度的定义及测试分析

为了对反射式电子阅读器的显示质量进行合理测评,本文探讨了3种常用的D65光源、D50光源和A光源下不同对比度的定义:计量材料本身的光谱行为的对比度定义为反射率对比度Cρ;计量材料的反光行为和人眼的接收特性的对比度定义为反射率视觉对比度Cv;计量材料本身的光谱行为,同时计量光源和人眼的光谱光效特性的对比度定义为亮度对比度CL。通过测试实验选择的电子阅读器产品分析不同对比度之间的关联特性。实验结果表明,在常用光源下,CL和Cv线性相关,在表征该类阅读器的黑白对比度性能上具有等同的作用,考虑到CL进一步可用于衡量黑白对比度的绝对大小。     

Improved antireflection properties of moth eye mimicking nanopillars on transparent glass: flat antireflection and color tuning

The sub-wavelength structures in moth eyes exhibit fascinating antireflective properties over the broadband wavelength region and at large incident angle by generating an air-mixed heterogeneous optical interface. In this work, antireflective behavior of transparent glass is observed with the elaborate controls of the nanopillar morphology. The reflectance spectrum shows a red shift and a notable light scattering with increase of the height of the nanopillars. The nanopillar arrays with a pointed cone shape have better optical performance in visible range than the rounded cone shape which is typical antireflective nanostructures in nature. Based on the observed antireflective behaviors, the flat and low value reflectance spectrum in the visible wavelength range is demonstrated by moth eye mimicking nanostructures on both sides of a glass surface. It is a unique strategy to realize a flat and broadband spectrum in the visible range showing 99% transparency via the appropriate matching of nanopillar height on the front and back sides of glass. The controlled reflection based color tuning on the antireflective and transparent glass is also obtained by adjusting the height of the nanopillar arrays on both sides. The visibility and self-cleaning ability of moth eye mimicking glass are examined for practical applications such as antireflection and self-cleaning.     

The n-type Ge photodetectors with gold nanoparticles deposited to enhance the responsivity

Gold nanoparticles (AuNPs) have been deposited on n-type Ge photodetectors to improve the responsivity. Two different coverage ratios, including 10.5 and 30.3% of AuNPs have been prepared, and the fabricated photodetectors are compared with the control sample. The 1,310-nm responsivities at -2 V of the control, 10.5% AuNPs, and 30.3% AuNPs samples are 465, 556, and 623 mA/W, respectively. The AuNPs could increase the responsivities due to the plasmon resonance. The reflectance spectra of these samples have been measured to verify that plasmon resonance contributes to the forward scattering of incident light. The reflectance decreases with AuNP deposition, and a denser coverage results in a smaller reflectance. The smaller reflectance indicates more light could penetrate into the Ge active layer, and it results in a larger responsivity.     

Influence of surface roughness on the diffuse to near‐normal viewing reflectance factor of coatings and its consequences on color measurements

In this work, we discuss the effect of surface roughness on the measurement of the diffuse to near‐normal viewing reflectance factor of coatings and evaluate its impact on the corresponding color coordinates. We compare specular component included (SCI) and excluded measurements. We introduce a gloss‐factor to account for surface roughness in specular component excluded measurements. We present experimental results on samples with different degrees of surface roughness. Samples in this study were chosen to expose the contribution of the surface in the reflectance factor. For slightly rough surfaces, the influence on the measured reflectance factor depends on whether the specular‐component is included or excluded. As the surface roughness increases, the specular‐excluded reflectance factor increases approaching its value with the SCI further roughness lead to similar measurement results in both configurations. © 2012 Wiley Periodicals, Inc. Col Res Appl, 38, 177–187, 2013.     

Colorimetry of durable fluorescent retroreflective materials

The development of durable daylight fluorescent retroreflective sheetings has led us to investigate some of the factors that influence color measurement of these materials. the colorimetry of retroreflective materials is particularly sensitive to measurement geometry. the added aspect of fluorescence increases the spectral uncertainties, making appearance measurements even more difficult. the visual properties used to describe fluorescent retroreflective materials should include chromaticity, lightness, peak spectral radiance factor, nighttime color, and color stability on exposure. A number of test methods exist for these measurements; however, practical experience in applying these methods to fluorescent materials shows significant variation in the resulting measured values. Colorimetric measurements on commercial instruments using 45/0 (0/45) geometry, a simulated D65 illuminant, and the CIE 2° standard observer yield results that are inadequate for precise quality control of durable fluorescent retroreflective materials. the uncertainty can be reduced by the use of transfer standards, provided that the standard is similar to the sample in both hue and fluorescent emission. Ultimately, the wide availability of commercial 2-monochromator spectrocolorimeters will be required. © 1995 John Wiley & Sons, Inc.